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  • 1
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 24 (1991), S. 1015-1022 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: X-ray diffraction studies are made on proton conducting polar lithium hydrazinium sulfate and ferroelectric lithium ammonium sulfate. The X-ray rocking curves recorded with in situ electric field along the polar b axis of lithium hydrazinium sulfate (direction of proton conductivity) show a strong enhancement of the 0k0 diffraction intensity. The corresponding 0k0 X-ray topographs reveal extinction contrast consisting of striations parallel to the polar axis. They disappear when the electric field is switched off. The effect is very strong in 0k0 but invisible in h0l reflections. It is present only if the electric field is parallel to the polar axis b. This unusual X-ray topographic contrast is correlated with the proton conduction. It is supposed that, under electric field, an inhomogeneous charge distribution develops, distorting the crystal lattice. Similar experiments on lithium ammonium sulfate also show contrast variations, but of quite different behaviour than before. In this case they result from changes of the ferroelectric domain configuration under electric field.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy Section 28 (1972), S. 871-876 
    ISSN: 0584-8539
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Durch Zusammensintern der Elemente bzw, der binären Sulfide wurde die gegenseitige Mischbarkeit in den Systemen CoCr2S4−NiCr2S4, CuCr2S4−NiCr2S4 und CoCr2S4−CuCr2S4 untersucht. In den Thiospinellen CoCr2S4 und CuCr2S4 können bis zu 20 (26) At% des Kobalts (Kupfers) durch Nickel substituiert werden (950°C), in das monokline NiCr2S4 wird nur wenig Kobalt bzw. Kupfer eingebaut. Zwischen dem halbleitenden, ferrimagnetischen Kobaltchromthiospinell und der metallisch leitenden, ferromagnetischen Kupferverbindung wurde lückenlose Mischkristallbildung beobachtet. Der von derVegardschen Regel abweichende Verlauf der Gitterkonstanten wird im Vergleich mit dem elektrischen und magnetischen Verhalten der Mischkristallreihe diskutiert.
    Notes: Abstract The miscibility within the systems CoCr2S4−NiCr2S4, CuCr2S4−NiCr2S4 and CoCr2S4−CuCr2S4 was studied by annealing the elements or binary sulphides. In the thiospinels CoCr2S4 and CuCr2S4, 20 per cent of cobalt and 26 per cent of copper, resp., can be substituted by nickel at 950°C. In monoclinic NiCr2S4, only small amounts of cobalt or copper are dissolved. The formation of a complete solid solution series was observed between the semiconducting ferrimagnetic CoCr2S4 and the metallic conducting ferromagnetic CuCr2S4. The deviation fromVegard's rule of lattice constants is discussed with respect to the electrical and magnetic behaviour of the solid solution series.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 83 (1971), S. 919-919 
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The infrared absorption and Raman spectra of SrCl2·2H2O powder as well as SrCl2·2D2O, and partially deuterated and isotopically dilute samples, have been recorded in the range from 30 to 4000 cm-1 at 95 and 295 K and analysed with regard to the strongly asymmetric force field in the H2O molecules. This is shown by an unusually large splitting of the OH and OD stretching fundamentals of the HDO molecules: 3426 and 3243 cm-1 and 2534 and 2408 cm-1 respectively at 95 K. Uncoupled OD stretching frequencies of SrCl2·6H2O and SrCl2·H2O are also presented. In SrCl2·2H2O both a relatively strong and a weak hydrogen bond to chloride ions are present; these are essentially straight.The spectra of SrCl2·2H2O exhibit the following characteristics: (1) no intramolecular coupling of the OH stretching vibrations; (2) very large Fermi resonance of νOH and 2δH2O; (3) the same high intensity of H2O twisting librations in the infrared spectra as for wagging and rocking modes; (4) splitting of the librational fundamentals of the HDO molecules, as large as 100 cm-1, caused by different structural arrangements of the H and D atoms in the asymmetric H2O molecules; and (5) strong intermolecular coupling of bending and librational fundamentals, which results in correlation splittings up to 75 cm-1. Possibilities of assigning the librational modes of H2O molecules which are in an asymmetric force field are discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Low temperature infrared and Raman spectra of polycrystalline BaBr2·2H2O at different degrees of deuteration are studied in the frequency range from 4000 to 30 cm-1. The single peaks observed for the bending fundamentals of isotopically dilute H2O and D2O show that the molecules of the water of crystallization are equivalent, as required by Bang's structure determination. The singlets observed for the three fundamentals of isotopically dilute HDO show that there is a symmetric force field in the water molecules which is not predicted from the structure determination. In BaBr2·2H2O weak hydrogen bonds to the bromine ions are present which are largely bent. From the shift of the stretching modes relative to the frequencies of free water the hydrogen bond enthalpy was found to be 20 kJ. The temperature shifts of all the stretching modes are positive, which is not in agreement with Falk's results on bent hydrogen bridges. The internal modes and the twisting libration of the water molecules show an unusual large correlation splitting due to intermolecular coupling of the vibrations of the two water molecules in the 2Br-·2H2O structure unit.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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